Amino group containing phenol

ABSTRACT

An object of the present invention is to provide a material which resolves the drawbacks associated with polyimide polymers, and yet retains the advantages offered by conventional polyimide polymers. 
     An amino group containing phenol derivative of the present invention is represented by a general formula (1) show below, and the present invention also provides a polyimide precursor produced using such an amino group containing phenol derivative.                  
 
(wherein, R 1 , R 2  and R 3 , which may be the same or different, each represent an alkyl group of 1 to 9 carbon atoms, an alkoxy group of 1 to 10 carbon atoms, a COOR group (in which R represents an alkyl group of 1 to 6 carbon atoms) or a hydrogen atom; R 4  and R 5 , which may be the same or different, each represent an alkyl group of 1 to 9 carbon atoms or a hydrogen atom; X represents —O—, —S—, —SO 2 —, —C(CH 3 ) 2 —, —CH 2 —, —C(CH 3 )(C 2 H 5 )—, or —C(CF 3 ) 2 —; and n represents an integer of 1 or greater).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an amino group containing phenolderivative, as well as a polyimide precursor or a polyimide polymer; aphotosensitive polyimide precursor or a photosensitive polyimidepolymer; and a composite material using the same.

2. Description of the Related Art

In recent years, advances in IT equipment functionality have created ademand for increased density within mobile equipment capable ofprocessing enormous quantities of information. Furthermore, considerablefocus is now being placed on the environmental impact of the materialsused in the production of these types of electronic components, and thedemands continue to become increasingly tight with calls for halogenfree flame proofing and improved heat resistance for lead free soldersand the like. Specific requirements include low stress, low dielectricconstant, high heat resistance, good adhesion and good flame resistance.Furthermore polyimide polymers, which are used conventionally inelectronic components for functions such as the surface protective filmsand interlayer insulation films of semiconductor elements, displayexcellent heat resistance, mechanical characteristics and flameresistance, as well as a low dielectric constant, good flame resistance,good ease of application, and good film forming properties, and as aresult have been widely mooted as potential materials for nextgeneration applications. However, current polyimide polymers havesignificant drawbacks including having poor adhesion (adhesiveness) withsilicon wafers and metal oxide and the like, and displaying a largedegree of thermal expansion following glass transition. Furthermore,modifications of polyimide polymers have proved difficult, and becausesuch polyimide polymers are also only sparingly soluble in organicsolvents, their workability is poor, and potential applications haveremained comparatively limited. In order to improve on these drawbacksassociated with polyimide polymers, Japanese Unexamined PatentApplication, First Publication No. Hei 5-255480 discloses well balancedepoxy modified polyimide polymers which are able to maintain theinherent heat resistance of the polyimide polymer while also ensuringgood flame resistance. In addition, Japanese Unexamined PatentApplication, First Publication No. Hei 6-345866 discloses siloxanemodified polyimide polymers in which a siloxane skeleton is introducedinto the main polyimide chain in order to produce lower stress values.

However, in the epoxy modified polyimide polymers disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 5-255480, themolecular weight, the ease of application and the mechanicalcharacteristics of the polyimide polymer actually deteriorate, and thedesired characteristics are not satisfactorily achieved. Furthermore, inthe siloxane modified polyimide polymers disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 6-345866, theheat resistance deteriorates as a result of the siloxane modification,and some loss occurs in the inherent characteristics of the originalpolyimide polymer. The present invention takes these issues intoconsideration, with an object of providing a material which resolves thedrawbacks associated with conventional polyimide polymers such as poorsubstrate adhesion and unsatisfactory flexibility, and yet retains theadvantages offered by conventional polyimide polymers.

SUMMARY OF THE INVENTION

The inventors of the present invention conducted intensive researchaimed at remedying the unsatisfactory characteristics of the polyimidepolymers described above, on the premise that complexes formed withother compounds may be effective in this regard. However, becauseconventional polyimide polymers and materials formed therefrom displaypoor reactivity with other compounds, this type of improvement provedextremely difficult. However on further investigation, the inventorsdiscovered that by introducing a phenol compound into a polyimidepolymer using an amino group containing phenol derivative, the formationof complexes with other compounds became possible, and theunsatisfactory characteristics of the polyimide polymer could beremedied by a complexed compound thereof, and were hence able tocomplete the present invention. In other words, an amino groupcontaining phenol derivative of the present invention is an amino groupcontaining phenol derivative represented by a general formula (1) showbelow.

(wherein, R¹, R² and R³, which may be the same or different, eachrepresent an alkyl group of 1 to 9 carbon atoms, an alkoxy group of 2 to10 carbon atoms, a COOR group (in which R represents an alkyl group of 1to 6 carbon atoms) or a hydrogen atom; R⁴ and R⁵, which may be the sameor different, each represent an alkyl group of 1 to 9 carbon atoms or ahydrogen atom; X represents —O—, —S—, —SO₂—, —C(CH₃)₂—, —CH₂—,—C(CH₃)(C₂H₅)—, or —C(CF₃)₂—; and n represents an integer of 1 orgreater.)

Furthermore, a polyimide precursor of the present invention is formedfrom a repeating unit represented by a general formula (2) shown below.

(wherein, R¹, R² and R³, which may be the same or different, eachrepresent an alkyl group of 1 to 9 carbon atoms, an alkoxy group of 2 to10 carbon atoms, a COOR group (in which R represents an alkyl group of 1to 6 carbon atoms) or a hydrogen atom; R⁴ and R⁵, which may be the sameor different, each represent an alkyl group of 1 to 9 carbon atoms or ahydrogen atom; X represents —O—, —S—, —SO₂—, —C(CH₃)₂—, —CH₂—,—C(CH₃)(C₂H₅)—, or —C(CF₃)₂—; R⁶ represents an aromatic tetracarboxylicdianhydride group; and n represents an integer of 1 or greater.)

Furthermore, a polyimide polymer of the present invention is obtainedvia a dehydration condensation reaction of an aforementioned polyimideprecursor. Furthermore, a polyimide precursor or a polyimide polymer ofthe present invention may also be a photosensitive polyimide precursoror a photosensitive polyimide polymer in which a hydrogen atom of atleast one phenolic hydroxyl group is substituted with a functional groupwhich imparts photosensitivity to the polyimide precursor. In addition,a polyimide precursor or a polyimide polymer of the present inventionmay also be complexed with another compound to form a composite material

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an IR spectrum of a product of a synthetic example 1.

FIG. 2 is an IR spectrum of a product of a synthetic example 2.

FIG. 3 is an IR spectrum of a product of a synthetic example 3.

FIG. 4 is an IR spectrum of a product of a synthetic example 4.

FIG. 5 is an IR spectrum of a product of a synthetic example 5.

FIG. 6 is an IR spectrum of a product of a synthetic example 6.

FIG. 7 is an IR spectrum of a product of an example 1.

FIG. 8 is an IR spectrum of a product of an example 2.

FIG. 9 is an IR spectrum of a product of an example 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As follows is a more detailed description of the composition of thepresent invention.

(A) Amino Group Containing Phenol Derivative

In an amino group containing phenol derivative according to theaforementioned general formula (1), the groups R¹, R², and R³, withinthe formula represent either:

-   (i) a straight chain or a branched chain alkyl group of 1 to 9    carbon atoms, and preferably 1 to 4 carbon atoms;-   (ii) an alkoxy group of 1 to 10 carbon atoms, and preferably 1 to 4    carbon atoms (in which the alkyl group of the alkoxy group may be    either a straight chain or a branched chain);-   (iii) a COOR group (in which R represents a straight chain or a    branched chain alkyl group of 1 to 6 carbon atoms, and preferably 3    to 6 carbon atoms); or-   (iv) a hydrogen atom, and the groups R¹, R², and R³ may be either    the same or different.

Of these options, the case in which R¹, R² and R³ represent alkyl groupsenables the water resistance to be improved. In the case of alkoxygroups or COOR groups, the adhesion of the compound to a substrate canbe improved, for those cases in which the compound is used in electroniccomponents, as described below. Furthermore, in the case of COOR groups,complexing with polyesters to form composite materials also becomespossible, as described below. In addition, hydrolysis of either thealkoxy groups or the COOR groups enables the alkali solubility to befurther improved, which is desirable for applications to alkalideveloping type uses. In other words, the groups R¹, R² and R³ shouldpreferably be selected in accordance with the desired application.Compounds in which either one or two of the groups R¹, R² and R³ arehydrogen atoms, and the remainder are groups other than hydrogen atoms,display particularly preferred characteristics. Furthermore, the groupor groups which are not hydrogen atoms should preferably be methylgroups. For example, combinations in which two of R¹, R², and R³ arehydrogen atoms and one is a methyl group, or combinations in which oneof R¹, R² and R³ is a hydrogen atom and the other two are methyl groupsproduce improvements in moisture resistance, and are consequentlypreferred.

In addition, the groups R¹, R² and R³ may be bonded to any of the carbonatom positions from 2 to 6 shown in the general formula (1), although incases in which a regular repeating unit is required, compounds with goodstructural symmetry are preferred. Particularly in those cases in whichtwo of the groups R¹, R² and R³, are hydrogen atoms and the other one isa group other than a hydrogen atom, bonding the non-hydrogen atom groupto the respective carbon atoms at position 4 generates better structuralsymmetry, and is consequently preferred for cases in which a regularrepeating unit is required. Furthermore, if all of the groups R¹, R² andR3 are methyl groups then the moisture resistance can be improved evenfurther, and the solubility in solvents also improves.

The groups R⁴ and R⁵ represent either a straight chain or a branchedchain alkyl group of 1 to 9 carbon atoms, and preferably 1 to 4 carbonatoms, or a hydrogen atom, and may be either the same or different. Byintroducing an alkyl group at R⁴ and/or R⁵ in this manner, the waterresistance of the compound can be improved. Furthermore, from theviewpoint of reactivity of the amino groups, R⁴ and R⁵ should preferablybe methyl groups.

In addition, if the R⁴ groups, the R⁵ groups, and the X and —CH₂— groupsbonded to the respective benzene rings comprising the two terminal aminogroups are bonded to the same number carbon atom in each case, and ifthe benzene rings to which the two terminal amino groups are bonded, andthe —X— and —CH₂— groups linking these benzene rings to the benzene ringor rings to which a phenolic hydroxyl group is bonded, are symmetricalin each case, then a high molecular weight polyimide precursor can beformed, which is desirable. X represents —O—, —S—, —SO₂—, —C(CH₃)₂—,—CH₂—, —C(CH₃)(C₂H₅)—, or —C(CF₃)₂—, although of these, a —CH₂— linkageresults in a simpler reaction process, and is consequently preferred. Ina preferred configuration, (i) the two R⁴ groups are each bonded to therespective carbon atom at either position 2 or position 6, (ii) the twoR⁵ groups are each bonded to the other respective carbon atom at eitherposition 2 or position 6, and (iii) X and the methylene group are eachbonded to the respective carbon atom at position 4. In such aconfiguration, because the hygroscopicity of the amino groups isguarded, the moisture resistance improves, and moreover because there isno interaction between the amino groups and an adjacent phenolichydroxyl group, the reactivity of the amino group increases, which isalso desirable.

n represents any integer of 1 or greater, although in actual practice isrestricted to an integer of no more than 20. Furthermore, integers of 1or greater, but no more than 15 are even more preferred. The actualvalue of n can be selected in accordance with the desiredcharacteristics of the final product.

Examples of the most preferred configurations for amino group containingphenol derivatives of the present invention are shown below.

(n is preferably from 1 to 20)

A production method for an amino group containing phenol derivative ofthe present invention is described below for the case in which X is a—CH₂— group in the aforementioned general formula (1). In the productionof this amino group containing phenol derivative, formalin is reactedwith a phenol based compound represented by a [formula a] shown below(namely, a compound based on the general formula (1) in which thebenzene rings to which the amino groups are bonded, X, and the methylenegroup have been excluded) and forms a dimethylolphenol derivativecontaining two bonded —CH₂OH groups, represented by a [formula b] shownbelow. In the general formula represented by the [formula b], if nrepresents a value of 2 or greater, then the structure comprises two ormore phenol based compounds connected via a methylene group. The valueof n can be varied depending on the characteristics of the raw materialphenol based compound represented by the [formula a], and the reactionconditions. Subsequently, the two —CH₂OH groups of this dimethylolphenolderivative are subjected to a condensation with the amino group of ananiline derivative represented by a [formula c] shown below, yieldingthe amino group containing phenol derivative represented by theaforementioned general formula (1).

The groups R¹, R², R³, R⁴ and R⁵, and the number n in the formulas from[formula a] through [formula c] are the same as those shown in thegeneral formula (1), and can be appropriately selected in accordancewith the desired amino group containing phenol derivative to beproduced.

As follows is a description of a specific example of the reactionconditions. A phenol based compound and an aqueous solution of formalin(preferably with a concentration of approximately 50 mass %) containing2 to 4 times the number of mols of the phenol based compound are placedin a reaction vessel equipped with a stirrer, a thermometer, a condenserand a dropping funnel, and with the mixture undergoing constantstirring, alkali is then added dropwise to the mixture under reactionconditions including a temperature of 0 to 50° C. and a reaction time of1 to 2 hours. The alkali is preferably an alkali aqueous solution ofsodium hydroxide or potassium hydroxide or the like, and can utilize,for example, an aqueous sodium hydroxide solution with a concentrationof approximately 30 mass %. Furthermore, the quantity of alkali istypically an equivalent number of mols to the phenol based compound.After addition of the alkali, the temperature is raised, and thereaction is allowed to proceed at a reaction temperature of 20 to 80° C.for a period of 2 to 4 hours.

Subsequently, the reaction mixture is cooled, preferably to atemperature of no more than 30° C., neutralized with acid, and theproduct is precipitated. There are no particular restrictions on theacid used, and a suitable example is an aqueous acetic acid solutionwith a concentration of approximately 10 mass %. The product is thenfiltered, washed with water, and then dried under reduced pressure,preferably at a temperature of no more than 50° C., yielding the product(a dimethylolphenol derivative). This product, together with an anilinederivative, an acid catalyst, and where necessary an organic solvent, isthen placed in a reaction vessel equipped with a thermometer, acondenser and a stirrer, and is reacted for a period of 4 to 8 hours ata temperature of 120 to 200° C., and preferably 140 to 180° C.

The quantity of the aniline derivative used should be 2 to 4 times, andpreferably 2.2 to 3.0 times the number of mols of the dimethylolphenolderivative. The acid catalyst may utilize any typical organic acid orinorganic acid, and suitable examples include hydrochloric acid,paratoluenesulfonic acid and oxalic acid, although of these, oxalic acidis preferred. The quantity of the acid catalyst can be alteredappropriately depending on the type of acid used, although in the caseof oxalic acid, a quantity of approximately 1 mass % relative to thetotal quantity of the materials in a reaction vessel is preferred.Furthermore, although an organic solvent is not a necessity, using asolvent such as an alcohol, a cellosolve or toluene is preferred. Thequantity of the solvent is typically from 10 to 20 mass % relative tothe total quantity of the reactants. Following reaction, the mixture iscooled, and then purified where necessary using known techniques such asdistillation or recrystallization, to yield an amino group containingphenol derivative according to the present invention. Examples ofsuitable solvents for the recrystallization include cellosolves,alcohols, acetate esters, benzene and toluene.

In those cases in which X in the aforementioned general formula (1) is alinkage group other than a —CH₂— group, an amino group containing phenolderivative can be produced by using a phenol based compound such asbisphenol-S, hydroxydiphenyl ether or bisphenol AF, and then performinga dimethylolation and reacting the product therefrom with an anilinederivative in the same manner as that described above.

(B) Polyimide Precursor and Polyimide Polymer

A polyimide precursor of the present invention is formed from arepeating unit represented by the aforementioned general formula (2).Furthermore, when this precursor is subjected to a dehydrationcondensation reaction, the two carboxyl groups and the imino groupbonded to the R⁶ group in the general formula (2) undergo respectivedehydration condensations, forming ring structures and generating apolyimide polymer formed from a repeating unit represented by a generalformula (3) shown below.

In the general formulas (2) and (3), the groups R¹, R², R³, R⁴, R⁵ andX, and the number n are the same as those described for theaforementioned amino group containing phenol derivative.

In the general formulas (2) and (3), R⁶ represents an aromatictetracarboxylic dianhydride group. Examples of preferred aromatictetracarboxylic dianhydrides include pyromellitic dianhydride,3,3′,4,4′-benzophenonetetracarboxylic dianhydride,2,2′,3,3′-benzophenonetetracarboxylic dianhydride,2,3,3′,4′-benzophenonetetracarboxylic dianhydride,naphthalene-2,3,6,7-tetracarboxylic dianhydride,naphthalene-1,2,5,6-tetracarboxylic dianhydride,naphthalene-1,2,4,5-tetracarboxylic dianhydride,naphthalene-1,4,5,8-tetracarboxylic dianhydride,naphthalene-1,2,6,7-tetracarboxylic dianhydride,3,3′,4,4′-diphenyltetracarboxylic dianhydride,2,2′,3,3′-diphenyltetracarboxylic dianhydride,2,3,3′,4′-diphenyltetracarboxylic dianhydride,3,3″,4,4″-p-terphenyltetracarboxylic acid,2,2″,3,3″-p-terphenyltetracarboxylic acid,2,3,3″,4″-p-terphenyltetracarboxylic acid,2,2-bis(2,3-dicarboxyphenyl)propane dianhydride,2,2-bis(3,4-dicarboxyphenyl)propane dianhydride,bis(2,3-dicarboxyphenyl) ether dianhydride,bis(2,3-dicarboxyphenyl)methane dianhydride,bis(3,4-dicarboxyphenyl)methane dianhydride,bis(2,3-dicarboxyphenyl)sulfone dianhydride,bis(3,4-dicarboxyphenyl)sulfone dianhydride,1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, and1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride. Of these compounds,pyromellitic dianhydride, 3,3′,4,4′-diphenyltetracarboxylic dianhydrideare particularly preferred as they represent the most typical examples,and also offer low degrees of thermal expansion.

The mass average molecular weights of the polyimide precursor and thepolyimide polymer fall within the same range. The mass average molecularweight of each can be appropriately adjusted in accordance with thedesired application of the product, although values from 10,000 to100,000 are preferred, and values from 20,000 to 60,000 are even moredesirable. By controlling the reaction conditions, polyimide precursorsor polyimide polymers according to the present invention can be producedwith good control over the mass average molecular weight, to produce avalue within the aforementioned range from 10,000 to 100,000, andpreferably from 20,000 to 60,000. As a result, a molecular weight whichcompares favorably with those of conventional polyimide polymers can beachieved.

Furthermore, in addition to having a similar mass average molecularweight to conventional polyimide polymers, it was discovered that apolyimide polymer of the present invention also has the extremely usefulcharacteristic of being soluble in organic solvents. In other words,typically, conventional aromatic polyimide polymers have been difficultto dissolve in organic solvents. As a result, typically a method isemployed in which a polyimide precursor (namely a polyamic acid) whichis soluble in organic solvents is prepared in advance, and a solutioncontaining this polyimide precursor dissolved in an organic solvent isthen applied to a substrate, and is subsequently converted to apolyimide by heating to cause a cyclodehydration and subsequent drying,thereby enabling the formation of a polyimide polymer film. Theconditions for the heating and drying treatment steps in this methodrequire a high temperature and a considerable length of time in order toachieve the cyclization of the polyimide precursor via a dehydrationcondensation and generate the product polyimide polymer. In contrast, apolyimide polymer of the present invention is soluble in organicsolvents, and consequently a polyimide polymer film can be produced byapplying a solution, not of a precursor, but rather of the polyimidepolymer itself generated by the dehydration condensation dissolved in anorganic solvent, and then performing a subsequent drying step at a farlower temperature and for a far shorter time period than the heating anddrying treatment conditions described above.

Consequently, a film can be produced in a far shorter time, and via afar simpler operation than is conventionally possible. Furthermore,because only a solvent removal treatment is required, and there is noneed to conduct a dehydration condensation reaction, a further benefitis obtained in that reductions in the film thickness or the generationof irregularities in the film thickness caused by dehydration do notoccur.

There are no particular restrictions on the organic solvent used,provided the solvent is capable of dissolving the polyimide polymers ofthe present invention, and either a single solvent, or a mixture of twoor more solvents may be used. Suitable solvents include organic solventssuch as N-methyl-2-pyrolidone, N,N-dimethylformamide,N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide,tetramethylene sulfone, γ-butyrolactone, and p-chlorophenol, as well asglyme based solvents such as methyldiglyme and methyltriglyme.

As described above, according to the present invention, polyimideprecursors and polyimide polymers can be provided which while retainingthe inherent advantages of conventional polyimide polymers, also offeradditional advantages in relation to film formation such as a simplerfilm formation process and a smoother film surface. In addition, apolyimide precursor of the present invention can be subjected to adehydration condensation reaction and converted to a polyimide polymer,before being dissolved in a solvent, applied to a substrate, andsubsequently dried to form a predetermined shape. Consequently, theproblem of dehydration condensation water being generated during theheating treatment, which arises in cases where a solution of a polyimideprecursor is first applied to a substrate, before being subjected to adehydration condensation reaction, can be avoided. As a result, voidsand the like, which can be generated during the removal of water from amolded product such as a film, are less likely to occur. In thin films,water generated by the dehydration condensation reaction can readilyescape into the atmosphere, but in the case of thicker films or thickermolded products in the shape of rectangular prisms or the like, thewater is far more difficult to remove, and voids and the like becomemore likely. In these types of applications, it is preferable that asolution containing a dissolved polyimide polymer is used, as a uniformmolded product with no voids can be produced. As a result, polyimideprecursors and polyimide polymers of the present invention, even withoutmixing, offer excellent characteristics as aqueous developing materials,adhesives for electronic materials, insulating materials, and moldingmaterials and the like.

A polyimide precursor of the present invention can be produced in themanner described below. First, an amino group containing phenolderivative and an organic solvent are placed in a reaction vessel, andthe mixture is stirred for approximately 30 minutes at room temperaturefor example, to dissolve the amino group containing phenol derivative.There are no particular restrictions on the organic solvent provided itis capable of uniformly dissolving the materials and reactants, andeither single solvents or mixtures of two or more solvents may be used.Suitable examples include organic solvents such asN-methyl-2-pyrolidone, N,N-dimethylformamide, N,N-dimethylacetamide,dimethylsulfoxide, hexamethylphosphoramide, tetramethylene sulfone,γ-butyrolactone, and p-chlorophenol, as well as glyme based solventssuch as methyldiglyme and methyltriglyme. Sufficient organic solvent isused to generate a concentration of the amino group containing phenolderivative of 10 to 35 mass %, and preferably 15 to 25 mass %.

Subsequently, with the temperature maintained at no more than 30° C.(and preferably at 20 to 25° C.), an aromatic tetracarboxylicdianhydride is added gradually with constant stirring, over a period of0.5 to 1 hour. The reaction mixture is then stirred at the sametemperature for a period of 1 to 20 hours, and yields a polyimideprecursor solution. In those cases in which the polyimide precursor isrequired, the solution should preferably be used, as is. The molar ratioof the amino group containing phenol derivative relative to the aromatictetracarboxylic dianhydride should be within a range from 1.2 to 0.9,and preferably approximately 1, and even more preferably from 1.01 to0.99.

In those cases in which the polyimide precursor is to be subsequentlysubjected to a dehydration condensation reaction to generate a polyimidepolymer, the polyimide precursor solution obtained in the mannerdescribed above is heated for 2 to 4 hours at a temperature of 170 to200° C., causing a dehydration condensation reaction and yielding apolyimide polymer.

(C) Photosensitive Polyimide Precursor and Photosensitive PolyimidePolymer

A photosensitive polyimide precursor of the present invention is apolyimide precursor formed from a repeating unit represented by theaforementioned general formula (2) in which the hydrogen atom of atleast one phenolic hydroxyl group is substituted with a functional groupwhich imparts photosensitivity to the polyimide precursor. Aphotosensitive polyimide polymer of the present invention is a polyimidepolymer formed from a repeating unit represented by the aforementionedgeneral formula (3) in which the hydrogen atom of at least one phenolichydroxyl group is substituted with a functional group which impartsphotosensitivity to the polyimide polymer. These photosensitivepolyimide precursors and photosensitive polyimide polymers displayexcellent characteristics as aqueous developing materials, as solderresists for electronic materials, and as photosensitive materials.Because this type of photosensitive polyimide polymer has alreadyundergone a dehydration condensation reaction prior to film formation,water is not generated during the film formation, which offers aconsiderable advantage in that the film thickness does not reduce duringthe film formation process. As described above for polyimide polymers ofthe present invention, a photosensitive polyimide polymer of the presentinvention is particularly effective in cases where water is difficult toremove, such as in thicker films.

When a photosensitive polyimide precursor is used in alkali developing,large quantities of photosensitive groups may need to be introduced inorder to achieve appropriate contrast during the alkali developingprocess. In the case of a photosensitive polyimide precursor, from 10 to90%, and preferably from 40 to 80% of the phenolic hydroxyl groupsshould be substituted with the aforementioned functional group whichimparts photosensitivity. In the case of a photosensitive polyimidepolymer, from 10 to 70%, and preferably from 20 to 40% of the phenolichydroxyl groups should be substituted with the functional group whichimparts photosensitivity.

The mass average molecular weights of the photosensitive polyimideprecursor and the photosensitive polyimide polymer fall within the samerange, and in order to achieve good applicability, values from 10,000 to100,000, and preferably from 20,000 to 60,000 are preferred.

Examples of functional groups which impart photosensitivity to polyimideprecursors or polyimide polymers include quinonediazide basedphotosensitive groups and acryloyl groups. Specific examples ofpreferred quinonediazide based photosensitive groups include1,2-benzoquinonediazide-4-sulfonate esters,1,2-naphthoquinonediazide-4-sulfonate esters,1,2-naphthoquinonediazide-5-sulfonate esters,2,1-naphthoquinonediazide-4-sulfonate esters, and2,1-naphthoquinonediazide-5-sulfonate esters.

As an example, a photosensitive polyimide precursor of the presentinvention substituted with a quinonediazide based photosensitive groupcan be produced by preparing a polyimide precursor of the presentinvention using the method described above, and then reacting 100 partsby mass of this precursor with preferably 1 to 50 parts by mass, andeven more preferably 5 to 25 parts by mass of quinonediazide sulfonylchloride. In this reaction, it is preferable that following the additionof the quinonediazide sulfonyl chloride, an additional 1.2 equivalentsof triethylamine is added dropwise over a period of approximately 30minutes, at a temperature of no more than 30° C., and preferably no morethan 25° C., and is subsequently reacted for a period of 2 to 12 hours.Subsequently, the reaction mixture is poured into a large volume of a0.2% aqueous oxalic acid solution, equivalent to 10 times the volume ofthe reaction solution, and the precipitated solid fraction is filtered,washed with ion exchange water and then dried to yield thephotosensitive polyimide precursor. In addition, a photosensitivepolyimide polymer of the present invention substituted with aquinonediazide based photosensitive group, for example, can be producedin a similar manner to that described above, by first preparing apolyimide polymer of the present invention, and then reacting this resinwith quinonediazide sulfonyl chloride in a similar manner to theaforementioned photosensitive polyimide precursor. Furthermore, aphotosensitive polyimide polymer can also be produced by subjecting anaforementioned photosensitive polyimide precursor to a dehydrationcondensation reaction. A photosensitive polyimide precursor or aphotosensitive polyimide polymer substituted with an acryloyl group canbe produced in the same manner as that described above, with theexception of replacing the quinonediazide sulfonyl chloride with acrylylchloride.

Although dependent to some degree on the desired final application ofthe product, the most preferred photosensitive polyimide precursors andphotosensitive polyimide polymers are those which use a preferred aminogroup containing phenol derivative shown in the above:

(n is preferably from 1 to 20). Of these, precursors and resins whichutilize pyromellitic dianhydride or 3,3′,4,4′-diphenyltetracarboxylicdianhydride as the aromatic tetracarboxylic dianhydride are particularlypreferred for those applications in which the effects of thermalexpansion are an important factor.(D) Composite Materials

Polyimide precursors and polyimide polymers of the present invention canbe converted to composite materials by complexing with other compounds.In the present invention, there are no particular restrictions on theseother compounds used in the formation of composite materials providedthey contain a functional group capable of reacting with a phenolichydroxyl group, and although the nature of the compound will varydepending on the application, synthetic resins and the like arepreferred. Specific examples include epoxy resins, silicone resins andacrylic resins, and these resins may be used singularly, or in mixturesof two or more different resins. In the present invention, compositematerials formed with epoxy resins or silicone resins can provideadditional favorable characteristics such as increased heat resistance,improved mechanical characteristics, electrical insulation and flameresistance of the polyimide polymer, as well as good film moldability,which are particularly desirable in electronic component applicationssuch as surface protective films for semiconductor elements andinterlayer insulation films and the like. Furthermore, in those cases inwhich any one of the groups R¹, R² and R³ in the general formulas (2)and (3) is a COOR group, composite materials can also be formed withpolyester resins. Of the polyimide precursors and the polyimidepolymers, complexing is possible for any precursor or resin which has atleast one phenolic hydroxyl group, and consequently complexing is alsopossible for photosensitive polyimide precursors or photosensitivepolyimide polymers with at least two phenolic hydroxyl groups, where aportion of the hydrogen atoms of these hydroxyl groups have beensubstituted with a quinonediazide based photosensitive group.

A composite material can be produced using the sample method describedbelow. First, a polyimide precursor or a polyimide polymer of thepresent invention and a compound for forming the composite material aremixed uniformly. In the case of a compound such as an epoxy resin with aglycidyl group, mixing is conducted for a period of 20 to 60 minutes,and preferably approximately 30 minutes, at a temperature of 40 to 80°C., and preferably a temperature of approximately 60° C. Subsequently, acatalyst such as triphenylphosphine, triethylamine or any other typicalcuring accelerator (although triphenylphosphine is preferred) is added,and the mixture is stirred for 20 to 60 minutes, and preferably forapproximately 30 minutes, at a temperature of 40 to 80° C., andpreferably a temperature of approximately 60° C., to cause thecomplexing reaction to proceed. The temperature is then raised to 170 to350° C., and that temperature is maintained for 3 to 5 hours to cure thematerial and produce the composite material. The curing can be conductedby, for example, maintaining a temperature of 180° C. for one hour,raising the temperature and then maintaining a temperature of 250° C.for a further one hour, and then raising the temperature again andmaintaining a temperature of 320° C. for yet another one hour. In thosecases where a film is to be formed, the composite material can beapplied to a substrate surface using spin coating or the like, prior tothe temperature raising and curing steps, and the material can then becured under similar conditions to those described above, enabling asubstrate bonded film to be produced with considerable ease.

The relative proportions of the polyimide precursor or polyimide polymerof the present invention and the other compound during the production ofa composite material can be altered appropriately in accordance with thenature of the other compound used and the intended final application,although in the case of the production of a composite material with asynthetic resin for example, ratios (mass ratios) within a range from10:1 to 1:10, and preferably from 4:1 to 1:4 are used.

In the case of complexing with an epoxy resin, there are no particularrestrictions on the type of epoxy resin, which can be selected inaccordance with the desired final application. Examples of suitableepoxy resins include phenol novolak type epoxy resins; o-cresol novolaktype epoxy resins; epoxides of bisphenol A, bisphenol S, bisphenol F andbiphenol and the like; and glycidylamine type epoxy resins formed byreaction of a polyamine such as diaminophenylmethane andepichlorohydrin, and these resins may be used singularly, or incombinations of two or more such resins. For example, in the case of anapplication to a molding material, any of the various novolak resins arepreferred, whereas in the case of applications to films or adhesives,dimer type epoxy resins using the various bisphenols are preferred. Theepoxy equivalence of the epoxy resin can be varied in accordance withthe intended application, although typical values are from 150 to 250,and preferably from 160 to 200. Composite materials formed by complexingan epoxy resin display a surprisingly large increase in the glasstransition point over the glass transition point of the polyimideprecursor prior to complexing, and the improvement in heat resistance ismarked. Accordingly, a material can be produced which not only has goodadhesion to electronic components such as substrates, but also displaysextremely good heat resistance.

For applications to electronic components, the epoxy resin shouldpreferably be selected from resins conventionally used in electroniccomponent applications. In such cases, the relative proportions of thepolyimide precursor or polyimide polymer of the present invention andthe epoxy resin are typically within a range from 4:1 to 1:4, andpreferably from 2:1 to 1:2 (mass ratios). Furthermore recently, filmlike materials have been proposed as IC sealing materials, and becausecomposite materials of the present invention display the excellent filmformation properties of a polyimide polymer, they can also be ideallyapplied to this type of application.

In the case of complexing with a silicone resin, there are no particularrestrictions on the type of silicone resin, which can be selected inaccordance with the desired final application. The number averagemolecular weight of the silicone resin can be altered in accordance withthe intended application, although typical values are within a rangefrom 3,000 to 30,000, and preferably from 5,000 to 20,000. Recently,with the increasing degree of integration in electronic components,silicone resins are being used as low stress resins. Accordingly, bycomplexing a silicone resin, a film or the like can be produced whichoffers good flexibility and low stress, and also displays the favorablecharacteristics of a polyimide polymer, namely a high level of heatresistance, a favorable dielectric constant and good film formingproperties. In particular, the composite material has the favorable filmforming properties of a polyimide polymer, and also exhibits theflexibility of a silicone resin, and consequently is ideal forapplications such as film like sealing materials and flexible printedcircuit boards. In such cases, the silicone resin should preferably beselected from resins conventionally used in electronic componentapplications. Suitable examples include phenylmethyl silicone resin,methyl silicone resin and modified silicone resin. In such cases, therelative proportions of the polyimide precursor or polyimide polymer ofthe present invention and the silicone resin are typically within arange from 10:10 to 10:1, and preferably from 10:4 to 10:2 (massratios).

In this manner, by forming a polyimide precursor or a polyimide polymerusing an amino group containing phenol derivative of the presentinvention, the introduction of a phenolic hydroxyl group enablescomposite materials to be formed by complexing with other materials,while the favorable polyimide polymer characteristics such as heatresistance, mechanical characteristics, electrical insulation and flameresistance can be retained. What is described here as complexing refersto a reaction of an aforementioned phenolic hydroxyl group of an aminogroup containing phenol derivative group with a functional group ofanother compound, resulting in bond formation. Complexing with anotherresin enables the favorable characteristics of this other resin to beimparted to the composite material. Specifically, complexing with anepoxy resin results in a material with a low thermal expansioncoefficient and good adhesion to substrates such as glass, metals andmetal oxides. In contrast, complexing with silicone resins provides amaterial which offers good adhesion to silicon wafers and glass plates,and also displays excellent flexibility. Furthermore, in a polyimideprecursor or a polyimide polymer using an amino group containing phenolderivative of the present invention, the hydrogen atoms of phenolichydroxyl groups can be substituted with a functional group which impartsphotosensitivity to the polyimide precursor or polyimide polymer,enabling the preparation of a photosensitive polyimide precursor or aphotosensitive polyimide polymer.

EXAMPLES

As follows is a more detailed description of the present invention basedon a series of examples.

(Synthesis of Amino Group Containing Phenol Derivatives)

Synthetic Example 1

(1) Synthesis of a Dimethylolphenol Derivative

2,2′-methylenebis(4-methyl-6-hydroxymethylphenol) shown below wassynthesized as a dimethylolphenol derivative, in the manner describedbelow.

162 g of p-cresol and 360 g of a 50% aqueous formalin solution wereplaced in a 2 L four neck flask equipped with a thermometer, acondenser, a stirrer and a dropping funnel. 200 g of a 30 mass % aqueoussolution of NaOH was then added dropwise over a two hour period at atemperature of no more than 30° C. The temperature was then raised to60° C. and the mixture was reacted for 4 hours, before the temperaturewas once again cooled to a temperature of no more than 30° C. 900 g of a10 mass % aqueous acetic acid solution was then added dropwise toneutralize the reaction mixture, which precipitated a crude product.This crude product was filtered, washed with water (300 g of water wasused for each wash, and four separate washing operations wereperformed), and then dried under reduced pressure at a temperature ofless than 50° C. (approximately 40° C.) to yield the product. The yieldwas 200 g, and the product was a white powder.

(2) Synthesis of an Amino Group Containing Phenol Derivative

Using the product obtained above,2,2′-methylenebis{4-methyl-6-(3,5-dimethyl-4-aminobenzyl)phenol} shownbelow was synthesized as an amino group containing phenol derivative, inthe manner described below.

First, 200 g of the above product, 190 g of 2,6-dimethylaniline, 3.0 gof oxalic acid, and 20 g of ethylcellosolve were placed in a 500 ml fourneck flask equipped with a thermometer, a condenser, and a stirrer, andreacted for 4 hours at a temperature of 120° C. The reaction mixture wasthen cooled and recrystallized from 800 g of ethylcellosolve to yieldthe amino group containing phenol derivative. The yield was 315 g, andthe product was a pale yellow power. Identification of the compound wasperformed based on the mass spectrum, the IR spectrum, and the meltingpoint. The melting point was measured using a DSC 220 manufactured bySeiko Instruments Inc., on a sample size of 3 to 5 mg, using atemperature range of 20 to 550° C., and raising the temperature at arate of 10° C./min. The IR spectrum is shown in FIG. 1. The meltingpoint for the product was 201° C.

Synthetic Example 2

(1) Synthesis of a Dimethylolphenol Derivative

2,6-dihydroxymethyl-4-n-propylcarboxyphenol shown below was synthesized.

With the exception of altering the conditions described below, a productwas obtained using the same method as described in the syntheticexample 1. The product yield was 100 g of a white powder.

-   Initial reactants: 90 g of propyl p-hydroxybenzoate and 120 g of a    50 mass % aqueous formalin solution.-   Dropwise addition conditions: 67 g of a 30 mass % aqueous solution    of NaOH added over a two hour period at a temperature of no more    than 40° C.-   Raised temperature reaction conditions: 3 hours at 75° C.-   Neutralization conditions: 540 g of a 10 mass % aqueous acetic acid    solution.    (2) Synthesis of an Amino Group Containing Phenol Derivative

Using the product obtained above,2,6-bis(3,5-dimethyl-4-aminobenzyl)-4-n-propylcarboxyphenol) shown belowwas synthesized as an amino group containing phenol derivative.

With the exception of altering the conditions described below, a productwas obtained using the same method as described in the syntheticexample 1. The product yield was 125 g of a pale yellow power. The IRspectrum is shown in FIG. 2. Furthermore, the melting point of theproduct was 127.8° C.

-   Initial reactants: 72 g of the above product, 80 g of    2,6-dimethylaniline, and 1.5 g of oxalic acid-   Reaction conditions: 4 hours at 140° C.

Synthetic Example 3

(1) Synthesis of a Dimethylolphenol Derivative

2,6-dihydroxymethyl-4-t-butylphenol shown below was synthesized as adimethylolphenol derivative.

With the exception of altering the conditions described below, a productwas obtained using the same method as described in the syntheticexample 1. The product yield was 67 g of a reddish yellow powder.

-   Initial reactants: 61 g of p-methoxyphenol and 162 g of a 37 mass %    aqueous formalin solution.-   Dropwise addition conditions: 67 g of a 30 mass % aqueous solution    of NaOH added over a two hour period at a temperature of no more    than 40° C.-   Raised temperature reaction conditions: 2 hours at 60° C.-   Neutralization conditions: 540 g of a 10 mass % aqueous acetic acid    solution.    (2) Synthesis of an Amino Group Containing Phenol Derivative

Using the product obtained above,2,6-bis(3,5-dimethyl-4-aminobenzyl)-4-t-butylphenol) shown below wassynthesized as an amino group containing phenol derivative.

With the exception of altering the conditions described below, a productwas obtained using the same method as described in the syntheticexample 1. The product yield was 120 g of a pale red solid. The IRspectrum is shown in FIG. 3. Furthermore, the melting point of theproduct was 180.7° C.

-   Initial reactants: 32 g of the above product, 30 g of    2,6-dimethylaniline, and 0.6 g of oxalic acid-   Reaction conditions: 4 hours at 140° C.-   Purification (recrystallization) conditions: 150 g of    ethylcellosolve.

Synthetic Example 4

(1) Synthesis of a Dimethylolphenol Derivative

A resol type orthocresol resin shown below was prepared as adimethylolphenol derivative.

With the exception of altering the conditions described below, a productwas obtained using the same method as described in the syntheticexample 1. The product yield was 100 g of a brown, viscous liquid.

-   Initial reactants: 81 g of o-cresol and 99 g of a 50 mass % aqueous    formalin solution.-   Dropwise addition conditions: 100 g of a 30 mass % aqueous solution    of NaOH added over a two hour period at a temperature of no more    than 30° C.-   Raised temperature reaction conditions: 1 hour at 70° C.-   Neutralization conditions: 450 g of a 10% aqueous acetic acid    solution.    (2) Synthesis of an Amino Group Containing Phenol Derivative

An orthocresol novolak with an aminobenzyl group at both terminals shownbelow was synthesized as an amino group containing phenol derivative.

First, 100 g of the above product, 180 g of aniline, and 2.8 g of oxalicacid were placed in a 500 ml four neck flask equipped with athermometer, a condenser, and a stirrer, and reacted for 4 hours at atemperature of 180° C. Any unreacted reactants were then removed over a30 minute period at −720 mmHg and 180° C. The product was then removedand yielded 250 g of a brown solid. The softening point was 113° C. TheIR spectrum is shown in FIG. 4. Furthermore, measurement of the massaverage molecular weight by GPC (gel permeation chromatography) revealeda value of 770.

(Synthesis of a Polyimide Precursor)

Synthetic Example 5

Using the amino group containing phenol derivative obtained in thesynthetic example 1, a polyimide precursor was synthesized in the mannerdescribed below.

4.940 g of the amino group containing phenol derivative obtained in thesynthetic example 1 and 40.30 g of NMP solvent (N-methylpyrolidone) wereplaced in a reaction vessel, and the amino group containing phenolderivative was dissolved by stirring for 30 minutes at room temperature.Subsequently, 2.180 g of pyromellitic dianhydride was added at atemperature of no more than 30° C. and the reaction mixture was thenstirred for 24 hours at a temperature of 25 to 28° C. to yield apolyimide precursor. The IR spectrum is shown in FIG. 5. The massaverage molecular weight of the product was 34,500.

(Synthesis of a Polyimide Varnish)

Synthetic Example 6

Using the amino group containing phenol derivative obtained in thesynthetic example 4, a polyimide varnish (a polyimide polymer solution)was synthesized in the manner described below.

6.180 g of the amino group containing phenol derivative obtained in thesynthetic example 4 and 32.57 g of NMP solvent were placed in a reactionvessel, and the amino group containing phenol derivative was dissolvedby stirring for 30 minutes at room temperature. Subsequently, 2.180 g ofpyromellitic dianhydride was added at a temperature of no more than 30°C., and the reaction mixture was stirred for one hour. Under anatmosphere of nitrogen, the temperature was then gradually raised to180° C. over a one hour period, and a dehydration condensation reaction(a cyclodehydration) was then performed over a 3 hour period to yield apolyimide varnish. The IR spectrum of the product is shown in FIG. 6.Furthermore, the mass average molecular weight of the product was32,000.

(Synthesis of a Polyimide Precursor for use in a Comparative Example 2,Described Below)

Synthetic Example 7

Using 4.00 g of p,p′-methylenedianiline, 4.36 g of pyromelliticdianhydride and 47.3 g of NMP solvent, a polyimide precursor wasprepared using the same method as that described for the syntheticexample 5.

(Synthesis of a Polyimide Precursor for use in a Comparative Example 3,Described Below)

Synthetic Example 8

20.0 g (0.10 mol) of p,p′-methylenedianiline and 6.00 g (0.001 mol) ofα,ω-bis(3-aminopropyl)polydimethylsiloxane with a mass average molecularweight of 6000 were dissolved in 272 g of NMP solvent, 22.02 g (0.101mol) of pyromellitic dianhydride was added, and the mixture was reactedfor 24 hours to yield a polyimide precursor.

Example 1 Complexing of the Polyimide Precursor of Synthetic Example 5and an Epoxy Resin

10 g of an epoxy resin (Epikote 828 (a brand name of Yuka Shell EpoxyCo., Ltd.)) and 50 g of the polyimide precursor produced in thesynthetic example 5 were mixed for 30 minutes at 60° C. to produce auniform mixture, and 0.1 g of triphenylphosphine was then added as acatalyst, and the mixture was stirred for a further 30 minutes at 60° C.The thus obtained composite polyimide precursor solution was applied toa silicon wafer and a Cu substrate using spin coating techniques, andthen subjected to heat treatment for 1 hour at 180° C. and 1 hour at250° C., to yield polyimide-epoxy complexed polymer film. The IRspectrum of this polyimide film is shown in FIG. 7. The polyimide filmcoated silicon wafer was then subjected to 48 hours of heat treatment ina pressure cooker at a temperature of 121° C. and 100% RH, and a crosscut peeling test was performed both prior to, and following this heattreatment (in Table, these results are recorded as “pre PCT” and “postPCT” respectively). The results revealed that peeling did not occur, andthat a good level of adhesion was maintained. The aforementioned crosscut peeling test is performed by using a cutter to cut the film into 100separate 5 mm×5 mm squares, sticking a cellophane adhesive tape to thefilm, and then pulling away the cellophane and recording the number ofsquares which are peeled away with the cellophane. The same test wasalso performed using the Cu substrate sample. The results are shown inTable 1.

The glass transition point, the thermal decomposition temperature(differential scanning calorimetry [DSC]), and the coefficient of linearthermal expansion were also measured for the above product, using thetechniques outlined below. The aforementioned composite polyimideprecursor solution was applied to aluminum foil by roll coating, andfollowing heat treatment, was peeled off the aluminum foil to yield afilm of thickness 50 μm. The glass transition point and the coefficientof linear thermal expansion were measured using this film. Specifically,the measurements were performed using a TMA (brand name, manufactured bySII), under conditions including a temperature of 200 to 400° C., a rateof temperature increase of 2° C./min., a loading of 10 g. The thermaldecomposition temperature was measured using a TG/DTA 320 (brand name,manufactured by SII), under conditions including a sample size of 10 mg,a temperature of 100 to 800° C., and a rate of temperature increase of10° C./min.

For the purposes of comparison, the polyimide precursor produced in thesynthetic example 7 was combined in a 1:1 ratio (mass ratio) with theepoxy resin used in the example 1, and then complexed in the same manneras described in the example 1, and the resulting product was subjectedto the same tests as above (comparative example 1). Furthermore, thesame tests were also performed on the uncomplexed general purposepolyimide polymer (comparative example 2). The glass transition pointwas also determined for the polyimide polymer produced by subjecting thepolyimide precursor of the example 1 to a dehydration condensationreaction. The results are shown in Table 1.

TABLE 1 Comparative Comparative Polyimide (prior Example 1 example 1example 2 to complexing) Glass transition point (° C.) 394 180 284 292Thermal decomposition 500 300 520 500 temperature (10% mass loss) (° C.)Coefficient of linear thermal 3.2 4.0 4.6 4.3 expansion (units: 10⁻⁴)Adhesion Tests (Cross cut peeling tests) Cu Pre PCT 100/100 22/100 0/100 0/100 Post PCT 100/100 0/100 0/100 0/100 Silicon wafer Pre PCT100/100 8/100 0/100 0/100 Post PCT 100/100 0/100 0/100 0/100

The results in Table 1 confirm that the composite material has a higherglass transition point and better heat resistance than the uncomplexedpolyimide polymer. Furthermore, the adhesion of the composite materialwas also excellent. In addition, the coefficient of linear thermalexpansion was small, and the variation in volume upon variations intemperature was also small.

Example 2 Complexing of the Polyimide Precursor of Synthetic Example 5and a Silicone Resin

2.0 g of a silicone resin (KF1001 (a brand name of Shin-Etsu ChemicalCo., Ltd.) and 50 g of the polyimide precursor produced in the syntheticexample 5 were mixed in a similar manner to the example 1, and 0.01 g oftriphenylphosphine was then added as a catalyst, and the resultingmixture was reacted for 1 hour at 150° C. A sample was then extracted,and a flexibility test was conducted in the manner described below. Theremaining reaction mixture was then reacted for a further 3 hours at180° C. to complete the reaction, and following cooling, was poured intoa large quantity of methanol. The precipitate that formed was filteredand dried and the resulting product was removed. The IR spectrum of theproduct is shown in FIG. 8. The formation of a complexed compositematerial was confirmed by the Si—O peak at 1000 to 1200 cm⁻¹. The massaverage molecular weight of the composite material was 37,000.Measurement of the glass transition point in a similar manner to theexample 1 produced a value of 260° C.

(Stress Measurement: Evaluation of Flexibility)

The polyimide precursor produced in the example 2 was spin coated on toa 5 inch silicon wafer, and then subjected to heat treatment for 3 hoursat 180° C. to form a polyimide film. The radius of curvature of the 5inch wafer was then measured, and the formula shown below was used tocalculate the stress on the silicon wafer. In addition, as a comparativeexample 3, the polyimide precursor produced in the synthetic example 8was also spin coated on to a 5 inch silicon wafer to form a polyimidefilm under the same conditions, and the radius of curvature of this 5inch wafer was also measured, and the formula shown below was used tocalculate the stress on the silicon wafer, in an identical manner. Theresults are shown in Table 2.$\sigma_{f} = {\frac{t_{s}^{2}}{6\; t_{f}R} \times \frac{E_{S}}{1 - r_{s}}}$

-   -   σ_(f): generated stress (kg/mm²)    -   t_(s): silicon wafer thickness (μm)    -   t_(f): film thickness (μm)    -   R: radius of curvature (μm)    -   E_(s): Young's modulus for silicon wafer (dyne/cm²)    -   r_(s): Poisson's ratio for silicon wafer (no units)

TABLE 2 Comparative Example 2 example 3 glass transition point 260 182(° C.) generated stress 2.0 2.1 (kg/mm²) film thickness 10 10

From the results in Table 2, it is evident that a combination of lowstress and a high glass transition point (heat resistance) has beenachieved in the example 2. In contrast, in the comparative example 3,although a low stress was achieved, the siloxane units of the mainskeleton have reduced the glass transition point, resulting in anunsatisfactory heat resistance.

Example 3 Synthesis of a Photosensitive Polyimide Polymer

26.7 g of the polyimide varnish produced in the synthetic example 6 wasplaced in a reaction vessel, 0.269 g of1,2-naphthoquinone-2-diazide-5-sulfonyl chloride was added, and themixture was stirred to produce a uniform mixture. With the reactionvessel cooled, 1.01 g of triethylamine diluted with acetone solvent to aconcentration of 10 mass % was then added dropwise over a 30 minuteperiod, and following completion of the addition, the reaction waspermitted to proceed for 24 hours at room temperature. Followingcompletion of the reaction, the reaction liquid was poured into 250 g ofa 0.02 mass % aqueous oxalic acid solution, and the precipitated yellowcolored solid was filtered, washed with ion exchange water, and thendried to yield a photosensitive polyimide polymer. The IR spectrum ofthis product is shown in FIG. 9. The IR spectrum confirmed that aphotosensitive group had been introduced into the resin. 3.0 g of thisphotosensitive polyimide polymer was dissolved in 12 g ofethylcellosolve to prepare a 20 mass % solution. This photosensitivepolyimide polymer solution was spin coated onto a silicon wafer, andfollowing heating for 10 minutes on a 90° C. hot plate, the filmthickness was measured and revealed a thickness of 5.2 μm. The film wasthen irradiated with 65 mJ/cm² of 365 nm radiation from a UV exposuredevice (ML-251C/A, manufactured by Ushio Inc.), subsequently immersed ina 1.98% aqueous TMAH solution (tetramethylammonium hydroxide) for 60seconds, and then washed with water for 20 seconds. The film thicknessof the exposed portion and the unexposed portion were measured, and aresidual film ratio was determined. The results were 0% for the exposedportion and 100% for the unexposed portion.

As described above, according to the present invention, by using anamino group containing phenol derivative with a phenolic hydroxyl group,composite materials can be formed with other compounds, and a variety ofmaterials can be provided which, while retaining the favorablecharacteristics of polyimide polymers, also display additionalcharacteristics not obtainable using solely a polyimide.

1. A polyimide precursor formed from a repeating unit represented by ageneral formula (2) shown below:

(wherein, R¹, R² and R³, which may be identical or different, eachrepresent an alkyl group of 1 to 9 carbon atoms, an alkoxy group of 1 to10 carbon atoms, a COOR group (in which R represents an alkyl group of 1to 6 carbon atoms) or a hydrogen atom; R⁴ and R⁵, which may be identicalor different, each represent an alkyl group of 1 to 9 carbon atoms or ahydrogen atom; X represents —O—, —S—, —SO₂—, —C(CH₃)₂—, —CH₂—,—C(CH₃)(C₂H₅)—, or —C(CF₃)₂—; R⁶ represents an aromatic tetracarboxylicdianhydride group; and n represents an integer of 1 or greater).
 2. Apolyimide precursor according to claim 1, wherein said R⁴ groups, saidR⁵ groups, and said X and —CH₂— groups bonded to respective terminalbenzene rings with bonded amino groups are bonded to an identicallynumbered carbon atom in each case (numbers showing carbon atom positionare shown in said general formula (2)).
 3. A polyimide precursoraccording to claim 1, wherein X is a —CH₂— group.
 4. A polyimideprecursor according to claim 1, wherein R⁴ and R⁵ are methyl groups. 5.A polyimide precursor according to claim 1, wherein either one or two ofR¹, R² and R³ are hydrogen atoms, and a remainder are groups other thanhydrogen atoms.
 6. A polyimide precursor according to claim 5, whereinsaid groups other than hydrogen atoms are methyl groups.
 7. A polyimideprecursor according to claim 1, wherein all of R¹, R² and R³ are methylgroups.
 8. A polyimide polymer obtained by performing a dehydrationcondensation reaction on a polyimide precursor according to claim
 1. 9.A photosensitive polyimide precursor, wherein a hydrogen atom of atleast one phenolic hydroxyl group of a polyimide precursor according toclaim 1 is substituted with a functional group which impartsphotosensitivity to said polyimide precursor.
 10. A photosensitivepolyimide polymer obtained by performing a dehydration condensationreaction on a photosensitive polyimide precursor according to claim 9.11. A photosensitive polyimide polymer, wherein a hydrogen atom of atleast one phenolic hydroxyl group of a polyimide polymer according toclaim 8 is substituted with a functional group which impartsphotosensitivity to said polyimide polymer.
 12. A composite materialobtained by complexing a polyimide precursor or a polyimide polymeraccording to claim 1 with another compound.
 13. A composite materialaccording to claim 12, wherein said another compound comprises an epoxyresin.
 14. A composite material according to claim 12, wherein saidanother compound comprises a silicone resin.